1. Field of Invention
The invention relates to a package seal inspection system for detecting air leaks in a sealed package.
2. Description of the Related Art
In certain packaging operations, it is necessary to maintain a substantially air tight seal between the tray or body of the package and a lid mounted thereon. This is particularly true in connection with food packaging wherein it is conventional to fill a tray with food and then heat seal a lid thereon. Although completely air tight seals are not required, it is desirable to detect leaks of a certain magnitude, known as gross leaks. For a typical package with a lid parameter of approximately 30 inches, any leak over one half inch is considered a gross leak.
Currently leak testing of food packages such as those used for frozen foods, is done manually. In such testing, an inspector presses down on a package lid and, if the lid offers sufficient resistance, according to the inspectors judgment, the package is deemed sufficiently air tight. If the lid yields easily, however, this indicates a gross leak and the product is discarded.
The manual system of testing for leaks has many disadvantages. It is expensive due to the cost in man hours and also results in inconsistent judgments due to the vagaries of the judgment of individual human beings. Moreover, individual inspectors are subject to fatigue and stress which are a major cause of the inability of the inspector to fully concentrate and remain alert. Consequently low quality products and low productivity result. The manual method for checking for leaks makes standardization very difficult, if not impossible.